Scratch can be accessed from scratch.mit.edu.
What is Scratch? A very popular drag and drop programming environment that is suitable for children 8 and up. There is an education specific site for Scratch at http://scratched.gse.harvard.edu/

Some years back the ScratchEd team also published a curriculum draft with twenty 60 minute lessons.

Want to get started with some simple Scratch projects? Here are some tutorials.

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Other interesting Scratch resources